In order to investigate the spatial and temporal diet variations of Coilia ectenes taihuensis, a special trawl and gill net were employed to sample fish in different ecotypic lakes (open water and aquatic-type zones) of Lake Taihu from February to December, 2013. In addition, feeding rate, fatness index and selectivity for different food items were examined for the purpose to study the growth and food preference of the fish. Observation of the gut contents indicated that C. ectenes taihuensis consumed a diverse assortment of prey, such as zooplankton, fish larvae, shrimp and aquatic insects, while cladocerans and copepods were the dominant components. The diet composition of C. ectenes taihuensis varied greatly with the seasons, pelagic copepod (mainly Calanoida and Cyclops) was the main prey in the winter, while pelagic cladocera (mainly Bosmina spp., Moina spp. and Chydorus spp.) was the dominant prey in the rest seasons. Compared with the two lake zones with different ecotypes, C. ectenes taihuensis in aquatic-type zone preyed more upon fish larvae, shrimp and aquatic insects and less upon copepod, while fish larvae and shrimp merely appeared in stomach of C. ectenes taihuensis with body length over 13.5 cm. The difference is obvious between the prey amounts of different sampling areas. 788.98±262.4 preys per fish were found in C. ectenes taihuensis stomach sampled from open water zone, while merely 298.85±71.1 preys per fish in aquatic-type zone. Feeding rates have a visible change with seasons, showing higher in the summer and winter and lower in the spring and autumn. The fish were willing to prey on large-sized cladocera, such as Daphnia cucullata, Simocephalus spp. and Daphnia magna, which the selectivity index(I_i) fluctuated between 0.59 and 1.00. In addition, C. ectenes taihuensis showed high selectivity (0.62< I_i< 0.95) for small-sized Moina spp., but a low selectivity for copepod due to their high escape capacity. The feeding habits of C. ectenes taihuensis varied greatly with seasons, but little with area, for example, C. ectenes taihuensis avoided preying on Leptodora spp. in winter but a high selectivity in summer. Gut content analysis of C. ectenes taihuensis help us to expound the cause of population growth based on food web theory, then provide effective measures to inhibit C. ectenes taihuensis population according to biomanipulation, and finally provide suggestions and foundations for adjusting freshwater fisheries structure and lake management.